Skype(539 Comments) - Plugins
What more can I say? It's the Skype API protocol plugin for Adium. Lets you bring through your Skype buddies into Adium and chat with them. (Needs Skype to be running to work)
More information, source files, recent updates,...

OkCupid(21 Comments) - Plugins
This is a protocol plugin for using the OkCupid chat in Adium. It's based on the libpurple plugin at http://okcupid-pidgin.googlecode.com/ (which in turn is based off the Facebook plugin)
If you're not seeing your buddy list in 2.06,...